Trade-offs between succulent and non-succulent epiphytes underlie variation in drought tolerance and avoidance

Epiphyte communities comprise important components of many forest ecosystems in terms of biomass and diversity, but little is known regarding trade-offs that underlie diversity and structure in these communities or the impact that microclimate has on epiphyte trait allocation. We measured 22 functional traits in vascular epiphyte communities across six sites that span a microclimatic gradient in a tropical montane cloud forest region in Costa Rica. We quantified traits that relate to carbon and nitrogen allocation, gas exchange, water storage, and drought tolerance. Functional diversity was high in all but the lowest elevation site where drought likely limits the success of certain species with particular trait combinations. For most traits, variation was explained by relationships with other traits, rather than differences in microclimate across sites. Although there were significant differences in microclimate, epiphyte abundance, and diversity, we found substantial overlap in multivariate trait space across five of the sites. We found significant correlations between functional traits, many of which related to water storage (leaf water content, leaf thickness, hydrenchymal thickness), drought tolerance (turgor loss point), and carbon allocation (specific leaf area, leaf dry matter content). This suite of trait correlations suggests that the epiphyte community has evolved functional strategies along with a drought avoidance versus drought tolerance continuum where leaf succulence emerged as a pivotal overall trait.

Abstract B50: MEK inhibitors mount a two-pronged attack to kill estrogen receptor positive (ER+) breast cancer cells undergoing hormonal therapy: Attenuated autophagy and induction of apoptosis

In a recent study, we identified the dephosphorylated form of BimEL as a key death effector of antiestrogen treatment of ER+ breast cancer cells and further showed that MEK1/MAPK1/2 blockade was required to produce high levels of dephosphorylated BimEL, particularly under conditions of insulin like growth factor 1 (IGF1) stimulation (Periyasamy-Thandavan et al., Breast Cancer Res. 14, 2012). Studies by others have identified MEK1/MAPK1/2 activation as essential to autophagy, a catabolic process induced by multiple stresses including ROS, ceramide accumulation, and nutrient deprivation. Autophagy induction results in autophagosome formation, trafficking of damaged proteins and mitochondria to the autophagosomes, and ultimately fusion with the lysosomes resulting in autolysosome formation. The autolysosome and its contents are degraded by the hydrolytic enzymes of the lysosome. Of particular interest to antiestrogen treatment of breast cancer, we and others have shown that pro-survival autophagy facilitates the emergence of antiestrogen resistant breast cancer cells. Thus, we are keenly interested in how MEK1/MAPK1/2 signaling affects pro-survival autophagy and if MEK blockade would be an effective approach toward blocking pro-survival autophagy in ER+ breast cancer cells undergoing hormonal treatment. In this study, we hypothesized that the requirement of MEK1/MAPK1/2 for pro-survival autophagy is due, in part, to its role in blocking the intracellular accumulation of dephosphorylated BimEL. To test this hypothesis, we modulated the expression of dephosphorylated BimEL with either a BimEL cDNA expression vector, siRNA targeting of BimEL, or MEK1 blockade with the small molecule inhibitor U0126 and determined the levels of the autophagic flux in ER+ breast cancer cells undergoing antiestrogen treatment. The determination of autophagic flux was made by comparing the levels of two proteins involved in autophagy -the LC3 /Atg8 and p62 (SQSTM1) proteins- in cell populations undergoing the different treatments in the presence or absence of chloroquine (CQ). The lipidated form of LC3, designated LC3II, is typically increased in cells undergoing autophagy, facilitates the formation of the mature autophagosomal membranes, and is subsequently degraded in the autolysosome. The p62 protein is required for the delivery of ubiquitinated protein complexes to the autophagosome and is degraded along with the ubiquitinated complex of proteins. CQ is a lysosomotrophic agent routinely used in autophagic flux assays because it blocks the turnover of autolysosomes with accumulation of LC3 II and p62, allowing the total levels of LC3II and p62 to be ascertained under all treatment conditions. These studies showed that siRNA targeting of BimEL increased basal and tamoxifen-induced autophagy in ER+ MCF-7 breast cancer cells. In contrast, the overexpression of dephosphorylated BimEL led to an increase in LC3 II and p62 levels due to a significant attenuation of autophagic flux (approximately 50%) in antiestrogen-treated cell populations. Current studies are focused on the mechanism of BimEL-mediated blockade of pro-survival autophagy, with the long term goal of optimizing this “downstream effector” function of MEK1/MAPK1/2 blockade in ER+ breast cancer cells for improved therapeutic outcome.

Citation Format: S. Takhar, M. Manning, A. Eason, M. Dix, S. Periyasamy-Thandavan, R. Padi, E. Bieberich, W. Hill, D. Browning, V. Ganapathy, M. Thangaraju, P. V. Schoenlein. MEK inhibitors mount a two-pronged attack to kill estrogen receptor positive (ER+) breast cancer cells undergoing hormonal therapy: Attenuated autophagy and induction of apoptosis. [abstract]. In: Proceedings of the AACR Special Conference on RAS Oncogenes: From Biology to Therapy; Feb 24-27, 2014; Lake Buena Vista, FL. Philadelphia (PA): AACR; Mol Cancer Res 2014;12(12 Suppl):Abstract nr B50. doi: 10.1158/1557-3125.RASONC14-B50

Behavior change in the funny papers: feedback to cartoonists on safety belt use

A multiple baseline across 8 nationally syndicated cartoonists evaluated the effects of personal advocacy letters encouraging presentations of a specific prevention message--the depiction of safety belt use in comic strips showing motor vehicle occupants. During baseline these cartoonists depicted safety belt use in only 15% (6 of 41) of their strips with occupied vehicles, but following receipt of a personal letter requesting safety belt use 41% (42 of 102) of their strips depicted safety belt use. Four cartoonists showed clear and immediate increases in depiction of safety belt use, 2 demonstrated delayed and somewhat less consistent belt use, and 2 cartoonists showed no change. The approach and results are discussed with regard to advocacy efforts intended to influence presentation of prevention messages in the media.